The invention relates to electrical cable connectors and particularly to such connectors intended for use with a jacketed metal clad cable assembly. Such cable assemblies contain a plurality of insulated wires that have a metal armor jacket disposed about the wires. An outer waterproof jacket, typically made of a thermoplastic material, is disposed around the armor jacket to exclude water or other foreign matter. In some forms of the invention the armor jacket may be in the form of a helical winding to increase the flexibility of the cable. The metal armor is grounded for safety reasons. Cables of this type may be used for transmitting power and/or control signals for use in distribution centers, motors, panel boards, and numerous other electrical and electromechanical apparatus.
The present connector is intended to terminate such metal clad cables and to connect to such apparatus. Such connectors must (1) provide a good electrical connection between the armor and the box, (2) a good seal to prevent water and other foreign matter from passing intermediate the connector and the cable, and (3) a good mechanical strength to secure the cable within the connector.
The prior art connector designs for this type of cable typically include a rubber grommet to seal out water and to mechanically connect the cable to the junction box. The conventional rubber grommet design uses a gland nut to compress the grommet axially. When the grommet is compressed axially the grommet sides are displaced radially inwardly and outwardly. This radial movement is typically utilized to seal and to hold the outside of the cable's armored jacket. The disadvantage of this design is that the range of the grommet is limited by the force the gland nut can apply to the grommet and the ability of the rubber to displace in a radially direction when subjected to an axial force. The displacement is the controlling factor in determining the ability of the grommet to seal and to hold the cable in position. The ability of the grommet to hold the cable in position is the limiting factor in determining the pullout force characteristic of the connector.
Twisting of the cable may be a problem when a connector utilizing a gland nut. More particularly, the torque applied to the nut may be transmitted to the grommet and cable.
Some other means of electrical connection is usually used to electrically connect or ground the armor jacket to the junction box via the body of the connector. Such means usually incorporate helical teeth, or thin flexible springs. The conventional methods of electrically connecting the armor jacket to the body include using resilient springs in conjunction with a mechanical force developed by pressing against the grommet. In order for the spring to be resilient and accept a wide range of cable the spring must be thin in order to be resilient. The spring thickness limits the cross sectional area of the electrical grounding path through the spring and could result in destruction of the ground path if the fitting was subjected to large ground fault currents. Other disadvantages of thin springs are the inherently low contact forces obtained with thin springs. The low contact forces and oxides that may form on the contact surfaces may in a poor electrical connections. Other typical conventional designs have cable twisting problems during installation.
One known construction is shown in U.S. Pat. No. 5,059,747. This construction suffers from the disadvantages described above.
It is an object of the invention to provide a cable connector that provides a reliable grounding connection to the armored cable.
Another object of the invention is to provide a connector that will not twist the wires within the cable when a connection is made.
Still another object is to provide a good seal to prevent water and other foreign matter from passing intermediate the connector and the cable.
A further object of the invention is to provide a good mechanical strength to secure the cable within the connector. In other words, the connector should have a high pullout strength.
Still another object of the invention is to provide a connector that is capable of cooperating with a large range of sizes of armored cable.
It is yet another object of the invention to provide apparatus that allows easy installation of a cable without disassembling the fitting.